1. Field of the Invention
Embodiments of the invention relate to laser patterning apparatuses and laser patterning methods.
2. Description of the Related Art
A thin-film photovoltaic device can be structured such that a plurality of photovoltaic elements are formed on an insulating substrate, where each photovoltaic element is formed of thin films of a first electrode layer, a photoelectric conversion layer, and a second electrode layer laminated at a single region. In addition, the first electrode of a photovoltaic element and the second electrode of the adjacent photovoltaic element are electrically connected in series to output a necessary voltage. The photovoltaic elements connected in series in this manner are formed by film forming and patterning of each layer and a combination of those. In the patterning, it is necessary to process a second patterning line to overlap a first patterning line obtained through the former processes. For this reason, the patterning demands high precision, and hence laser patterning with good processing precision is widely used.
Hitherto, a glass substrate has been used as the substrate of the thin-film photovoltaic device, but in recent years, a flexible substrate such as a plastic film is increasingly being used. The thin-film photovoltaic device using the flexible substrate is lightweight and has good operability. Furthermore, thanks to the flexibility, the thin-film photovoltaic device can be massively produced by a roll-to-roll method.
However, warpage, looseness, wrinkles, and the like easily occur in the flexible substrate, and flatness of the laser processing surface easily deteriorates. For this reason, in the flexible substrate, the processing precision of the laser patterning easily deteriorates as compared with the glass substrate.
Therefore, when the laser patterning is performed on a thin film formed on the surface of the flexible substrate, as disclosed in Japanese Patent Application Laid-Open No. 10-15686 (see paragraph [0019] and FIG. 4) and Japanese Patent Application Laid-Open No. H08-90271 (see paragraph [0010] and FIG. 4), the laser patterning is performed in a manner such that the flexible substrate is disposed on a processing stage in a state in which both ends of the flexible substrate are stretched by the tension applied in the direction perpendicular to the transporting direction.
However, in some cases, warpage, looseness, wrinkles, and the like are not sufficiently removed even if tension is applied to both ends of the flexible substrate in the direction perpendicular to the transporting direction. For example, there is a need to increase tension to remove the looseness or the warpage when the looseness or the warpage of the flexible substrate is large. However, wrinkles easily occur along the transporting direction when the tension increases. In addition, the linearity, the line width, or the like deteriorates, product defects occur, and the yield thereof deteriorates when the laser patterning is performed in the presence of the wrinkles and the like.